Semiconductor device and method of manufacturing the same

ABSTRACT

In a semiconductor device, via holes are formed around a chip buried in a package, one end of a conductor filled in the via hole is covered with a pad portion exposed to the outside, and a wiring layer connected to the other end of the conductor is formed. The portion (pad portion) of the wiring layer which correspond to the conductor is exposed from a protective film, or an external connection terminal is bonded to the top of the pad portion. Electrode terminals of the chip are connected to the wiring layer, and the opposite surface of the chip is exposed to the outside.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority of Japanese PatentApplication No. 2004-011666 filed on Jan. 20, 2004, the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a semiconductor device and a method ofmanufacturing the same. More specifically, the present invention relatesto a semiconductor device having a package structure in which asemiconductor element (chip) is mounted within a wiring board for areduction in thickness, and relates to a method of manufacturing thesame.

(b) Description of the Related Art

Heretofore, semiconductor devices having various forms have beenproposed in which a chip is mounted within a wiring board. As anexample, there is a package structure (semiconductor device) intended toform a required circuit block by incorporating and stacking a pluralityof chips, for example, typified by System Block Module manufactured byToshiba Corporation Semiconductor Company. In this semiconductor device,connection between upper and lower layers is established around chips.Accordingly, on the upper and lower surfaces of each package,top-and-bottom connecting pads are placed around the chip. Thetop-and-bottom connecting pads are used for connecting packages (chips)stacked on and under the relevant package (chip). Most of thetop-and-bottom connecting pads are connected also within the relevantpackage. In such a semiconductor device, plated through holes have beentypically used as means for connecting the top-and-bottom connectingpads within the package.

Technologies relating to the above-described known technology include,for example, as described in Japanese unexamined Patent Publication(JPP) 2001-217337, a technology with which multilayer stacking can berealized by burying and mounting a semiconductor chip in a package, andproviding external connection terminals on both surfaces of the package,or exposing, from a solder resist layer, terminal formation portions(pad portions) of a wiring pattern to which external connectionterminals are to be connected.

As described above, in a known package structure (semiconductor device)adapted for the stacking of a plurality of chips using top-and-bottomconnecting pads provided in a region around the chips, plated throughholes have been used when the top-and-bottom connecting pads areconnected within the package.

However, plated through holes are often formed by drilling.Consequently, the diameters of the through holes become relatively large(approximately 250 to 300 μm in the state of the art), and there hasbeen a disadvantage in that a larger area is accordingly required.Further, there are constraints on design (i.e., the degree of freedom ofwiring is low), such as the technical difficulty of placingtop-and-bottom connecting pads on plated through holes. Accordingly, therelevant pads must be formed at other positions, and thus an arearequired around the chip increases. This has become an obstacle tominiaturization.

Essentially, one of major purposes in stacking chips is to enhancefunctionality by incorporating a larger number of functional elements(chips) into a smaller volume. However, the above-described problembecomes a serious obstacle to the accomplishment of this purpose.Namely, in a package (semiconductor device) containing a chip, a regionaround the chip is not a portion which exerts an essential function asthe semiconductor device, but a portion used for simply connecting upperand lower stacked packages. Accordingly, in consideration of recentdemands for smaller sizes, higher densities, and the like, of thin-typepackages, it is more desirable that an area required around the chip isas small as possible.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor deviceand a method of manufacturing the semiconductor device in which when asemiconductor element (chip) is mounted within a package,miniaturization is realized and the degree of freedom of wiring isincreased, in which a three-dimensional arrangement configuration ofchips and connections therebetween can be easily realized as needed, andconsequently which contributes to an enhancement of functionality.

To attain the above object, according to one aspect of the presentinvention, there is provided a semiconductor device including: a wiringboard; and at least one semiconductor element buried in the wiringboard, wherein the wiring board has an insulating base material; one endof a conductor filled in a via hole which is formed in a region aroundthe semiconductor element to pierce the insulating base material in athickness direction is covered with a first pad portion which is made ofconductive material and which is exposed to one surface of theinsulating base material; a wiring layer which has a required patternshape and which is connected to another end of the conductor is formedon another surface of the insulating base material; and a protectivefilm covering the wiring layer and the insulating base material isformed with a second pad portion exposed, the second pad portion beingdelimited in a portion of the wiring layer which corresponds to theconductor, and wherein at least part of electrode terminals of thesemiconductor element is electrically connected to the second padportion of the wiring layer; and a surface thereof opposite to a surfacehaving the electrode terminals formed thereon is exposed to one surfaceof the insulating base material.

In the semiconductor device according to this aspect, the semiconductorelement (chip) is buried and mounted within the wiring board used as apackage, and the via hole piercing the wiring board vertically (in thethickness direction) is formed in a region around the chip. The via holecan be formed to have a small diameter, for example, by laserprocessing, compared with a through hole formed by drilling asheretofore. This means that an area required around the chip can berelatively reduced, and contributes to a miniaturization of the package(semiconductor device).

Moreover, since the via hole is filled with the conductor, the first padportion (top-and-bottom connecting pad) can be placed thereon (on oneend of the conductor). Namely, compared with the case where a platedthrough hole is formed as heretofore and where a top-and-bottomconnecting pad cannot be placed thereon and must be formed at anotherposition, the degree of freedom of wiring can be increased. Further,since the relevant pad does not need to be formed at another position,an area required around the chip can be accordingly reduced. Thiscontributes to a further miniaturization of the package (semiconductordevice).

Furthermore, devices according to the present aspect can be stacked in amultilayered manner by using the first and second pad portionsrespectively exposed from both surfaces of the package (semiconductordevice) as top-and-bottom connecting pads, and as needed, by interposingexternal connection terminals therebetween. Accordingly, it is possibleto easily realize a three-dimensional arrangement configuration of chipsand connections therebetween. This contributes to an enhancement offunctionality.

Also, according to another aspect of the present invention, there isprovided a method of manufacturing a semiconductor device, including thesteps of: forming a first pad portion made of conductive material at aspecific position around a semiconductor element mount region on onesurface of a conductive base material; mounting a semiconductor elementon the semiconductor element mount region; forming an insulating basematerial on the conductive base material to bury the semiconductorelement therein; forming a first via hole in the insulating basematerial so as to reach the first pad portion; filling the first viahole with a conductor; forming a second via hole at a specific positionin the insulating base material so as to reach an electrode terminal ofthe semiconductor element; forming a wiring layer having a requiredpattern shape on the insulating base material so as to fill the secondvia hole and to be connected to the conductor filled in the first viahole; forming a protective film which covers the wiring layer and theinsulating base material in such a way that a second pad portion isexposed, the second pad portion being delimited in a portion of thewiring layer which corresponds to the conductor; and removing theconductive base material.

Also, according to still another aspect of the present invention, thereis provided a method of manufacturing a semiconductor device, includingthe steps of: forming a recessed portion in a portion of one surface ofa conductive base material which corresponds to a specific positionaround a semiconductor element mount region, and then forming a firstpad portion made of conductive material on a surface of the recessedportion; mounting a semiconductor element on the semiconductor elementmount region; forming an insulating base material on the conductive basematerial to bury the semiconductor element therein; forming a first viahole in the insulating base material so as to reach the first padportion; filling the first via hole with a conductor; forming a secondvia hole at a specific position in the insulating base material so as toreach an electrode terminal of the semiconductor element; forming awiring layer having a required pattern shape on the insulating basematerial so as to fill the second via hole and to be connected to theconductor filled in the first via hole; forming a protective film whichcovers the wiring layer and the insulating base material in such a waythat a second pad portion is exposed, the second pad portion beingdelimited in a portion of the wiring layer which corresponds to theconductor; and removing the conductive base material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of asemiconductor device according to a first embodiment of the presentinvention;

FIGS. 2A to 2F are cross-sectional views showing manufacturing steps forthe semiconductor device of FIG. 1;

FIGS. 3A to 3E are cross-sectional views showing manufacturing stepssubsequent to the manufacturing steps of FIGS. 2A to 2F;

FIG. 4 is a cross-sectional view showing the structure of asemiconductor device according to a second embodiment of the presentinvention;

FIGS. 5A to 5F are cross-sectional views showing manufacturing steps forthe semiconductor device of FIG. 4;

FIGS. 6A to 6E are cross-sectional views showing manufacturing stepssubsequent to the manufacturing steps of FIGS. 5A to 5F;

FIG. 7 is a cross-sectional view showing the structure of asemiconductor device according to a third embodiment of the presentinvention;

FIGS. 8A to 8F are cross-sectional views showing manufacturing steps forthe semiconductor device of FIG. 7;

FIGS. 9A to 9E are cross-sectional views showing manufacturing stepssubsequent to the manufacturing steps of FIGS. 8A to 8F;

FIG. 10 is a cross-sectional view showing the structure of asemiconductor device according to a fourth embodiment of the presentinvention;

FIG. 11 is a cross-sectional view showing the structure of asemiconductor device according to a fifth embodiment of the presentinvention; and

FIG. 12 is a cross-sectional view showing the structure of asemiconductor device according to a sixth embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a cross-sectional structure of asemiconductor device according to a first embodiment of the presentinvention.

The semiconductor device 10 according to this embodiment includes awiring board 20 used as a package, and a semiconductor element (silicon(Si) chip) 30 buried in the package (wiring board) 20. In the exampleshown in the drawing, one semiconductor chip 30 is buried in onepackage. However, two or more semiconductor chips 30 may beappropriately buried therein depending on functions required for thepresent device 10.

In the package (wiring board) 20, reference numeral 21 denotes aninsulating base material (e.g., a resin layer made of epoxy resin) whichserves as a base for the wiring board. In this resin layer 21, via holesVH1 piercing the resin layer 21 in the thickness direction are formed ina region around the semiconductor chip 30. These via holes VH1 arefilled with conductors 22 (e.g., metal such as copper (Cu)). At one end(lower surface in the example shown in the drawing) of the individualconductor 22, a pad portion 23 which has a slightly larger diameter thanthat of the via hole VH1 and which is made of conductive material (e.g.,palladium (Pd), gold (Au)) is formed. The pad portion 23 is exposed toone surface (lower surface) of the resin layer 21. Further, on the othersurface (upper surface) of the resin layer 21, a Cu wiring layer 24which is connected to the other end of the conductor 22 and which has apredetermined pattern shape is formed. The portion of the wiring layer24 which corresponds to the conductor 22 is delimited as a pad portion24P. Furthermore, a protective film 25 (e.g., solder resist layer) isformed in such a manner that the entire surfaces of the wiring layer 24and the resin layer 21 are covered, except for the regions of the padportions 24P, and external connection terminals 26 (e.g., solder bumps)are bonded to the respective tops of the pad portions 24P.

The external connection terminals 26 are provided in the example shownin the drawing, but do not necessarily need to be provided. It isessential only that part of the wiring layer 24 (the pad portions 24P)is exposed from the solder resist layer 25 so that external connectionterminals can be bonded thereto when necessary. Further, the externalconnection terminals 26 are provided only on one surface (upper surface)of the package (wiring board) 20 in the example shown in the drawing,but may be provided on both surfaces of the package (wiring board) 20 asneeded. In this case, the external connection terminals 26 are alsobonded to the pad portions 23 on the lower side.

On the other hand, as for the semiconductor chip 30, at least some ofthe electrode terminals 31 thereof are electrically connected to the padportions 24P via the wiring layer 24 filled in the via holes VH2. Theback surface (surface opposite to the surface on which the electrodeterminals 31 are formed) of the semiconductor chip 30 is covered with aninsulating layer 32 exposed to one surface (lower surface) of the resinlayer 21. Further, it is desirable that a semiconductor chip having athickness as small as possible is used as the semiconductor chip 30because the semiconductor chip 30 is mounted within the package (wiringboard) 20. In the state of the art, semiconductor chips havingthicknesses of approximately 50 μm to 100 μm have been developed. It issufficiently possible to bury a semiconductor chip having such athickness within the board. Accordingly, in the present embodiment, athin semiconductor chip having a thickness of approximately 50 μm isused as the semiconductor chip 30.

The semiconductor device 10 according to the present embodiment has thefollowing features: the thin semiconductor chip 30 is buried within thepackage (wiring board) 20; the via holes VH1 formed around thesemiconductor chip 30 are filled with the conductors 22; andtop-and-bottom connecting pads (pad portions 23 and 24P) are formed ordelimited on the conductors 22, thus making it possible to realizemultilayer stacking using the top-and-bottom connecting pads as needed,as described later.

Hereinafter, a method of manufacturing the semiconductor device 10according to the first embodiment will be described with reference toFIGS. 2 A to 3E which show manufacturing steps thereof in order.

To begin with, in the first step (FIG. 2A), copper foil 27 is preparedas a conductive base material.

In the next step (FIG. 2B), the pad portions 23 which have diameters ofapproximately 150 μm and which are made of conductive material areformed at specific positions (positions corresponding to portions inwhich via holes to be described later are to be formed) around asemiconductor element mount region MR on one surface (upper surface inthe example shown in the drawing) of the copper foil 27. For example,the specific positions on the copper foil 27 (Cu) are plated with nickel(Ni) as an underlying layer and then plated with palladium (Pd), and,furthermore, the tops thereof are plated with gold (Au) as needed, thusforming the pad portions 23.

When the pad portions 23 are formed, a die pad portion having the sameplating constitution as the pad portions 23 may be formed in thesemiconductor element mount region MR as indicated by a dashed line inthe drawing.

In the next step (FIG. 2C), the thin semiconductor chip 30 having athickness of approximately 50 μm is mounted on the semiconductor elementmount region MR on the copper foil 27 with the insulating layer 32interposed therebetween. For example, non-conductive paste (NCP) isapplied to the semiconductor element mount region MR, or anon-conductive film (NCF) is attached to the semiconductor element mountregion MR, and the semiconductor chip 30 is bonded thereto with the NCPor the NCF in the state where the surface of the semiconductor chip 30which is opposite to the surface having the electrode terminals 31formed thereon is faced down. Alternatively, insulating resin, such asunderfill resin to be filled into a space between a chip and a mountboard in flip-chip mounting, may be used.

In the next step (FIG. 2D), the resin layer 21 is formed on the copperfoil 27 in such a manner that the semiconductor chip 30 is buried. Forexample, the resin layer 21 is formed using thermosetting resin, such asepoxy to be used as interlayer insulating material when a build-upprinted circuit board is manufactured. Alternatively, instead of epoxyresin, polyimide resin may be used. This resin layer 21 functions as aninsulating base material for the package (wiring board) 20.

In the next step (FIG. 2E), the via holes VH1 reaching the pad portions23 are formed at specific positions (positions corresponding to theportions in which the pad portions 23 are formed) of the resin layer 21.For example, the via holes VH1 having small diameters (of approximately100 μm) can be easily formed by removing the corresponding portions ofthe resin layer 21 using a CO₂ laser, an excimer laser, or the like.

In the next step (FIG. 2F), the via holes VH1 are filled with theconductors 22. For example, conductive paste containing metal, such ascopper (Cu), is filled into the via holes VH1, or electrolytic Cuplating is performed using the copper foil 27 as a power supplyinglayer, thus filling the via holes VH1.

In the next step (FIG. 3A), similar to the process performed in the stepof FIG. 2E, the via holes VH2 reaching the electrode terminals 31 of thesemiconductor chip 30 are formed at specific positions (positionscorresponding to the electrode terminals 31 of the buried semiconductorchip 30) of the resin layer 21 by laser processing.

In the next step (FIG. 3B), the wiring layer 24 having a requiredpattern shape is formed on the resin layer 21 so as to fill the viaholes VH2 on the semiconductor chip 30 and to be connected to theconductors 22 filled in the via holes VH1 around the semiconductor chip.Specifically, a thin metal film is formed on the entire surface of theresin layer 21 including the insides of the via holes VH2 by sputtering,electroless plating, or the like, and a pattern (wiring layer 24) isformed by a subtractive method, a semi-additive method, or the like,using the thin metal film as a seed. For example, the entire surface ofthe resin layer 21 including the insides of the via holes VH2 is madeinto a catalyst, electroless Cu plating is performed to a thickness ofapproximately 3 μm (formation of the thin metal film), then a platingpattern is formed of a plating resist. The surface of the thin metalfilm is electrolytically plated with Cu by pattern plating using thethin metal film as a power supplying layer, then the plating resist isremoved, and thereafter unnecessary Cu is etched using the pattern madeby electrolytic Cu plating as a mask, thus forming a Cu pattern (wiringlayer 24).

Furthermore, the top of the wiring layer 24 (Cu) is plated with Ni/Au asneeded. This is intended to improve the adhesiveness to the wiring layerwhen solder bonding is performed in a later step.

In the next step (FIG. 3C), the solder resist layer 25 is formed tocover the wiring layer 24 and the resin layer 21 in such a manner thatthe portions (pad portions 24P) of the wiring layer 24 which correspondto the conductors 22 are exposed. For example, photosensitive solderresist is applied to the entire surfaces of the wiring layer 24 and theresin layer 21. Exposure and development are performed in accordancewith the shapes of the required pad portions 24P (patterning of solderresist), and openings are formed in the portions of the solder resistlayer which correspond to the regions of the pad portions 24P. Thus, thepad portions 24P of the wiring layer 24 are exposed, and the otherportion of the wiring layer 24 is covered with the solder resist layer25. The solder resist layer 25 functions as a protective film for thepackage (wiring board) 20.

In the next step (FIG. 3D), the solder bumps 26 as external connectionterminals are formed on the pad portions 24P (Cu) exposed from thesolder resist layer (protective film) 25. The solder bumps 26 can beformed, for example, by plating. Alternatively, the following method maybe adopted: after flux is applied to the pad portions 24P, solder ballsare mounted thereon, or solder paste is supplied thereto by printing,and the solder balls or the solder paste is made into bumps by reflow ata temperature of approximately 240° C. to 260° C. In this case, foraftertreatment, the surface is cleaned to remove the flux.

In the last step (FIG. 3E), the copper foil 27 used as the conductivebase material is removed by wet etching. Thus, the semiconductor device10 according to the first embodiment is manufactured.

As described above, according to the first embodiment (FIGS. 1 to 3E),the semiconductor chip 30 is buried within the wiring board 20 used as apackage, and the via holes VH1 are formed at specific positions aroundthe semiconductor chip 30 by laser processing. Accordingly, thediameters of the via holes VH1 can be made small compared with those ofthrough holes formed by drilling as heretofore. Incidentally, in thestate of the art, the diameters of through holes are approximately 250to 300 μm, whereas, in the present embodiment, the diameters of the viaholes VH1 can be made as small as approximately 100 μm. Thus, an arearequired around the semiconductor chip 30 becomes relatively small.Accordingly, the package 20 (semiconductor device 10) can beminiaturized.

Further, since the via holes VH1 are filled with the conductors 22, thepad portions 23 (top-and-bottom connecting pads) can be placed on theconductors 22. In other words, the degree of freedom of wiring can beincreased compared with the following case: plated through holes areformed as heretofore, and therefore top-and-bottom connecting padscannot be placed thereon and must be formed at other positions. Inaddition, since the relevant pads do not need to be formed at otherpositions, an area required around the semiconductor chip 30 can beaccordingly reduced. This contributes to a further miniaturization ofthe package 20 (semiconductor device 10).

Moreover, the packages according to the present embodiment can bestacked in a multilayered manner as needed, as described later, by usingthe pad portions 23 and 24P respectively exposed from both surfaces ofthe package 20 (semiconductor device 10) as top-and-bottom connectingpads or by interposing the external connection terminals (solder bumps26) bonded to the tops of the pad portions 24P. Accordingly, athree-dimensional arrangement configuration of the semiconductor chips30 and connections therebetween can be easily realized. This contributesto an enhancement of functionality of a semiconductor device.

Furthermore, although the external connection terminals (solder bumps26) do not necessarily need to be provided as described above, theprovision of the external connection terminals has the followingadvantage. Specifically, since the formation of the external connectionterminals (solder bumps 26) in the step of FIG. 3D makes it possible toconduct tests of functions, operations, and the like, of the package 20(semiconductor device 10) in which the semiconductor chip 30 is buried,the relevant package can be rejected as a defective package at thisstage if the relevant package does not pass the tests. Namely, onlynon-defective packages (semiconductor devices) can be picked up. Thismakes it possible to increase yield on a product (semiconductor device)basis when non-defective packages are stacked in a multilayer structureto be modularized as described later.

FIG. 4 schematically shows a cross-sectional structure of asemiconductor device according to a second embodiment of the presentinvention.

In this embodiment, similar to the first embodiment (FIG. 1), thesemiconductor device 10 a includes a wiring board 20 a used as apackage, and the semiconductor chip 30 buried in the package (wiringboard) 20 a. The package (wiring board) 20 a in this embodiment differsfrom the package (wiring board) 20 in the first embodiment in that aresin layer 21 a is formed in such a manner that the exposed surface ofthe insulating layer 32 protrudes from one surface (surface in which thepad portions 23 are formed) of the resin layer 21 a. Other componentsand functions thereof are the same as those of the first embodiment, andthus the explanation thereof is omitted.

Further, in a method of manufacturing the semiconductor device 10 a ofthis embodiment, part of manufacturing steps thereof are also differentbecause of the features of the above-described constitution. Namely, themanufacturing method (FIGS. 5A to 6E) according to this embodimentdiffers from the manufacturing method (FIGS. 2A to 3E) according to thefirst embodiment in that when the pad portions 23 are formed at specificpositions around the semiconductor element mount region on one surfaceof the copper foil 27 in the step of FIG. 5B, a recessed portion RP1 isfurther formed in the portion corresponding to the semiconductor elementmount region by half-etching. Since the recessed portion RP1 is formedin the portion corresponding to the semiconductor element mount region,the surface in which the insulating layer 32 is formed protrudes fromthe surface in which the pad portions 23 are formed when the resin layer21 a is formed in a later step (FIG. 5D). Namely, if the thickness ofthe resin layer 21 a on the semiconductor chip 30 is equal to that(thickness of the resin layer 21) in the case of the first embodiment,the thickness of the resin layer 21 a on the pad portions 23 becomesrelatively small. Accordingly, when the via holes VH1 are formed in alater step (FIG. 5E), the depths of the via holes VH1 are relativelyreduced. Other steps are basically the same as those for the case of thefirst embodiment, and thus the explanation thereof is omitted.

According to the second embodiment (FIGS. 4 to 6E), in addition tovarious advantages obtained in the first embodiment, the depths of thevia holes VH1 formed around the semiconductor chip 30 can also bereduced (specific advantage to the second embodiment) based on thefeatures of the above-described constitution. Namely, since the laserirradiation time can be reduced, the diameters of the via holes VH1 canbe further reduced. This contributes to a further miniaturization of thepackage 20 a (semiconductor device 10 a).

FIG. 7 schematically shows a cross-sectional structure of asemiconductor device according to a third embodiment of the presentinvention.

In this embodiment, similar to the second embodiment (FIG. 4), thesemiconductor device 10 b includes a wiring board 20 b used as apackage, and the semiconductor chip 30 buried in the package (wiringboard) 20 b. The package (wiring board) 20 b in this embodiment differsfrom the package (wiring board) 20 a in the second embodiment in thatone end of the conductor 22 b filled in the via hole VH1 protrudes fromone surface (lower surface in the example shown in the drawing) of aresin layer 21 b, and that the pad portion 23 b is formed to follow theshape of the protruded surface (convex surface) of the conductor 22 b.Other components and functions thereof are the same as those of thesecond embodiment, and thus the explanation thereof is omitted.

Further, in a method of manufacturing the semiconductor device 10 b ofthis embodiment, part of manufacturing steps thereof are also differentbecause of the features of the above-described constitution. Namely, themanufacturing method (FIGS. 8A to 9E) according to this embodimentdiffers from the manufacturing method (FIGS. 5A to 6E) according to thesecond embodiment in the following points: in the step of FIG. 8B, arecessed portion RP1 and recessed portions RP2 are formed byhalf-etching in the portion of one surface of the copper foil 27 whichcorresponds to the semiconductor element mount region and in theportions thereof which correspond to specific positions around thesemiconductor element mount region, respectively; and furthermore, thepad portions 23 b are formed on the surfaces of the recessed portionsRP2. Since the recessed portions RP2 are formed in the portions wherethe pad portions 23 b are to be formed, one end of the conductor 22 bprotrudes from one surface (lower surface) of the resin layer 21 b whenthe conductor 22 b is filled into the via hole VH1 in a later step (FIG.8F). Other steps are basically the same as those for the case of thesecond embodiment, and thus the explanation thereof is omitted.

According to the third embodiment (FIGS. 7 to 9E), in addition tovarious advantages obtained in the second embodiment (the advantagesobtained in the first embodiment and the advantage specific to thesecond embodiment), the amount of solder used for the connection betweenpackages can also be decreased based on the features of theabove-described constitution when packages 20 b (semiconductor devices10 b) according to the present embodiment are stacked in a multilayerstructure to be modularized, because the pad portions 23 b protrude.

Further, if solder is filled into the recessed portions RP2 byelectrolytic solder plating, instead of forming the pad portions 23 b onthe recessed portions RP2 in the step of FIG. 8B, solder bumps asexternal connection terminals of the semiconductor device 10 b can befinally constituted.

Incidentally, in the constitution (FIG. 7) according to the thirdembodiment, similar to the constitution (FIG. 4) according to the secondembodiment, the exposed surface of the insulating layer 32 protrudesfrom one surface (surface in which the pad portions 23 b are formed) ofthe resin layer 21 b. However, it is a matter of course that the exposedsurface of the insulating layer 32 does not necessarily need to beprotruded. For example, similar to the constitution (FIG. 1) accordingto the first embodiment, the exposed surface of the insulating layer 32may be formed to be positioned in the same plane as one surface of theresin layer 21 b.

FIGS. 10 to 12 schematically show cross-sectional structures ofsemiconductor devices according to fourth to sixth embodiments,respectively.

The semiconductor devices 40, 40 a, and 40 b (FIGS. 10, 11, and 12)according to the fourth, fifth, and sixth embodiments each have astacked structure in which semiconductor devices 10, 10 a, or 10 b(FIGS. 1, 4, or 7) according to the first, second, or third embodimentare stacked in three layers to be modularized, respectively. In each ofthe semiconductor devices 40, 40 a, and 40 b, two vertically adjacentsemiconductor devices 10, 10 a, or 10 b are electrically connected toeach other via the top-and-bottom connecting pads (pad portions 23 or 23b) of one semiconductor device and the external connection terminals(solder bumps 26) of the other, and bonded together using underfillresin 41 filled in the space between both devices.

Further, in the semiconductor device 40 (FIG. 10) according to thefourth embodiment, the semiconductor device 10 in the uppermost layerhas no external connection terminals (solder bumps 26) provided therein,and the semiconductor device 10 in the middle layer has the externalconnection terminals (solder bumps 26) provided only on one surface(upper surface) thereof, and the semiconductor device 10 in the lowestlayer has the external connection terminals (solder bumps 26) providedon both surfaces thereof.

Further, in the semiconductor device 40 a (FIG. 11) according to thefifth embodiment, the semiconductor device 10 in the uppermost layer hasthe external connection terminals (solder bumps 26) provided only on onesurface (lower surface) thereof, and each of the semiconductor devices10 a in the middle and the lowest layers has the external connectionterminals (solder bumps 26) provided on both surfaces thereof.

Moreover, in the semiconductor device 40 b (FIG. 12) according to thesixth embodiment, the semiconductor device 10 b in the uppermost layerhas no external connection terminals (solder bumps 26) provided therein,and the semiconductor device 10 b in the middle layer has the externalconnection terminals (solder bumps 26) provided only on one surface(upper surface) thereof, and the semiconductor device 10 b in the lowestlayer has the external connection terminals (solder bumps 26 and 26 b)provided on both surfaces thereof. In this case, the amount of solderused for the solder bumps 26 b on the lower side of the semiconductordevice 10 b in the lowest layer is relatively small because the padportions 23 b protrude in convex shapes.

Incidentally, in each of the semiconductor devices 40, 40 a, and 40 baccording to the fourth, fifth, and sixth embodiments, description hasbeen made taking as an example the case where the semiconductor devices10, 10 a, or 10 b according to the first, second, or third embodimentsare stacked in three layers to be a multilayer structure. However, it isa matter of course that the number of stacked layers is not limited tothree. Namely, the number of stacked layers can be appropriatelyselected according to functions required for a semiconductor devicehaving a modularized stacked structure.

Further, in each of the constitutions according to the fourth to sixthembodiments, the external connection terminals (solder bumps 26 or 26 b)for the entire stacked structure (40, 40 a, or 40 b) are provided in thesemiconductor device (10, 10 a, or 10 b) in the lowest layer. However,in contrast to this, the relevant external connection terminals may beprovided in the semiconductor device in the uppermost layer.

1. A semiconductor device comprising: a wiring board; and at least onesemiconductor element buried in the wiring board, wherein the wiringboard has an insulating base material; one end of a conductor filled ina via hole which is formed in a region around the semiconductor elementto pierce the insulating base material in a thickness direction iscovered with a first pad portion which is made of conductive materialand which is exposed to one surface of the insulating base material; awiring layer which has a required pattern shape and which is connectedto another end of the conductor is formed on another surface of theinsulating base material; and a protective film covering the wiringlayer and the insulating base material is formed with a second padportion exposed, the second pad portion being delimited in a portion ofthe wiring layer which corresponds to the conductor, and wherein atleast part of electrode terminals of the semiconductor element iselectrically connected to the second pad portion of the wiring layer;and a surface thereof opposite to a surface having the electrodeterminals formed thereon is exposed to one surface of the insulatingbase material.
 2. The semiconductor device according to claim 1, whereinan external connection terminal is bonded to at least one of the firstand second pad portions.
 3. The semiconductor device according to claim2, wherein the insulating base material is formed in a state where thesurface of the semiconductor element opposite to the surface having theelectrode terminals formed thereon protrudes from the one surface of theinsulating base material.
 4. The semiconductor device according to claim1, wherein the one end of the conductor filled in the via hole protrudesfrom the one surface of the insulating base material, and the first padportion is formed to follow a shape of a protruded surface of theconductor.
 5. The semiconductor device according to claim 1, wherein thesurface of the semiconductor element opposite to the surface having theelectrode terminals formed thereon is covered with any one of aninsulating layer and a die pad portion which is exposed to the onesurface of the insulating base material.
 6. A semiconductor devicecomprising a plurality of stacked semiconductor devices, each beingaccording to claim 2, wherein two adjacent semiconductor devices areconnected via the external connection terminal.
 7. A method ofmanufacturing a semiconductor device, comprising the steps of: forming afirst pad portion made of conductive material at a specific positionaround a semiconductor element mount region on one surface of aconductive base material; mounting a semiconductor element on thesemiconductor element mount region; forming an insulating base materialon the conductive base material to bury the semiconductor elementtherein; forming a first via hole in the insulating base material so asto reach the first pad portion; filling the first via hole with aconductor; forming a second via hole at a specific position in theinsulating base material so as to reach an electrode terminal of thesemiconductor element; forming a wiring layer having a required patternshape on the insulating base material so as to fill the second via holeand to be connected to the conductor filled in the first via hole;forming a protective film which covers the wiring layer and theinsulating base material in such a way that a second pad portion isexposed, the second pad portion being delimited in a portion of thewiring layer which corresponds to the conductor; and removing theconductive base material.
 8. The method according to claim 7, furthercomprising, between the step of forming a protective film and the stepof removing the conductive base material, a step of bonding an externalconnection terminal to the second pad portion of the wiring layer. 9.The method according to claim 7, wherein in the step of forming a firstpad portion made of conductive material at a specific position around asemiconductor element mount region on one surface of a conductive basematerial, an recessed portion is further formed in a portioncorresponding to the semiconductor element mount region.
 10. A method ofmanufacturing a semiconductor device, comprising the steps of: forming arecessed portion in a portion of one surface of a conductive basematerial which corresponds to a specific position around a semiconductorelement mount region, and then forming a first pad portion made ofconductive material on a surface of the recessed portion; mounting asemiconductor element on the semiconductor element mount region; formingan insulating base material on the conductive base material to bury thesemiconductor element therein; forming a first via hole in theinsulating base material so as to reach the first pad portion; fillingthe first via hole with a conductor; forming a second via hole at aspecific position in the insulating base material so as to reach anelectrode terminal of the semiconductor element; forming a wiring layerhaving a required pattern shape on the insulating base material so as tofill the second via hole and to be connected to the conductor filled inthe first via hole; forming a protective film which covers the wiringlayer and the insulating base material in such a way that a second padportion is exposed, the second pad portion being delimited in a portionof the wiring layer which corresponds to the conductor; and removing theconductive base material.
 11. The method according to claim 10, furthercomprising, between the step of forming a protective film and the stepof removing the conductive base material, a step of bonding an externalconnection terminal to the second pad portion of the wiring layer. 12.The method according to claim 10, wherein in the step of forming a firstpad portion made of conductive material at a specific position around asemiconductor element mount region on one surface of a conductive basematerial, an recessed portion is further formed in a portioncorresponding to the semiconductor element mount region.